A diesel particulate filter ( DPF ) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine .
84-510: OPF may refer to: Science and technology [ edit ] Gasoline particulate filter (German: Ottopartikelfilter Otto particle filter), capturing soot particles from the petrol engine exhaust gases OEB Package Format , an eBook format OpenProject Foundation, the foundation for the open source web-based application OpenProject , registered 2012 in Berlin, Germany Optimal power flow ,
168-415: A power-valve system . The valves are normally in or around the exhaust ports. They work in one of two ways; either they alter the exhaust port by closing off the top part of the port, which alters port timing, such as Rotax R.A.V.E, Yamaha YPVS, Honda RC-Valve, Kawasaki K.I.P.S., Cagiva C.T.S., or Suzuki AETC systems, or by altering the volume of the exhaust, which changes the resonant frequency of
252-421: A rotary valve is that it enables the two-stroke engine's intake timing to be asymmetrical, which is not possible with piston-port type engines. The piston-port type engine's intake timing opens and closes before and after top dead center at the same crank angle, making it symmetrical, whereas the rotary valve allows the opening to begin and close earlier. Rotary valve engines can be tailored to deliver power over
336-421: A DKW design that proved reasonably successful employing loop charging. The original SAAB 92 had a two-cylinder engine of comparatively low efficiency. At cruising speed, reflected-wave, exhaust-port blocking occurred at too low a frequency. Using the asymmetrical three-port exhaust manifold employed in the identical DKW engine improved fuel economy. The 750-cc standard engine produced 36 to 42 hp, depending on
420-537: A byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter. DPF filters go through a regeneration process which removes this soot and lowers the filter pressure. There are three types of regeneration: passive, active, and forced. Passive regeneration takes place normally while driving, when engine load and vehicle drive-cycle create temperatures that are high enough to regenerate
504-448: A crossflow engine) is always best and support is good. In some engines, the small end is offset to reduce thrust in the intended rotational direction and the forward face of the piston has been made thinner and lighter to compensate, but when running backward, this weaker forward face suffers increased mechanical stress it was not designed to resist. This can be avoided by the use of crossheads and also using thrust bearings to isolate
588-470: A patent in 1880 in Germany. The first truly practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott , who started producing twin-cylinder water-cooled motorcycles in 1908. Two-stroke gasoline engines with electrical spark ignition are particularly useful in lightweight or portable applications such as chainsaws and motorcycles. However, when weight and size are not an issue,
672-449: A scavenging function. The units run in pairs, with the lower half of one piston charging an adjacent combustion chamber. The upper section of the piston still relies on total-loss lubrication, but the other engine parts are sump lubricated with cleanliness and reliability benefits. The mass of the piston is only about 20% more than a loop-scavenged engine's piston because skirt thicknesses can be less. Many modern two-stroke engines employ
756-658: A similar system. Traditional flywheel magnetos (using contact-breaker points, but no external coil) worked equally well in reverse because the cam controlling the points is symmetrical, breaking contact before top dead center equally well whether running forward or backward. Reed-valve engines run backward just as well as piston-controlled porting, though rotary valve engines have asymmetrical inlet timing and do not run very well. Serious disadvantages exist for running many engines backward under load for any length of time, and some of these reasons are general, applying equally to both two-stroke and four-stroke engines. This disadvantage
840-434: A spark-ignited engine, which typically has less than 0.5% oxygen in the exhaust gas stream before the emission control device(s), diesel engines have a very high ratio of oxygen available. While the amount of available oxygen makes fast regeneration of a filter possible, it also contributes to runaway regeneration problems. Some applications use off-board regeneration. Off-board regeneration requires operator intervention (i.e.
924-424: A special cement so that heat expansion of the core will be taken up by the cement, and not the package. SiC cores are usually more expensive than cordierite cores, however they are manufactured in similar sizes, and one can often be used to replace the other. Silicon carbide filter cores also look like catalytic converter cores that have had alternate channels plugged – again the plugs force the exhaust gas flow through
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#17327754845461008-428: A store. There are a variety of devices that produce over 50% particulate matter filtration, but less than 85%. Partial filters come in a variety of materials. The only commonality between them is that they produce more back pressure than a catalytic converter, and less than a diesel particulate filter. Partial filter technology is popular for retrofit. Filters require more maintenance than catalytic converters. Soot,
1092-460: A technique used to simulate load flow through an AC power system Other uses [ edit ] Miami-Opa Locka Executive Airport (IATA and FAA LID: OPF), Florida, US Orbiter Processing Facility , a class of hangars at Kennedy Space Center, Florida, US Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title OPF . If an internal link led you here, you may wish to change
1176-518: A turbocharger. Crankcase-compression two-stroke engines, such as common small gasoline-powered engines, are lubricated by a petroil mixture in a total-loss system . Oil is mixed in with their petrol fuel beforehand, in a fuel-to-oil ratio of around 32:1. This oil then forms emissions, either by being burned in the engine or as droplets in the exhaust, historically resulting in more exhaust emissions, particularly hydrocarbons, than four-stroke engines of comparable power output. The combined opening time of
1260-493: A variety of strategies: All on-board active systems use extra fuel, whether through burning to heat the DPF, or providing extra power to the DPF's electrical system, although the use of a fuel borne catalyst reduces the energy required very significantly. Typically a computer monitors one or more sensors that measure back pressure and/or temperature, and based on pre-programmed set points the computer makes decisions on when to activate
1344-492: A wide range of engine operating conditions. Since the continuous flow of soot into the filter would eventually block it, it is necessary to 'regenerate' the filtration properties of the filter by burning off the collected particulate on a regular basis. Soot particulate burn-off forms water and CO 2 in small quantities amounting to less than 0.05% of the CO 2 emitted by the engine. Some cores are made from metal fibers – generally
1428-400: A wider speed range or higher power over a narrower speed range than either a piston-port or reed-valve engine. Where a portion of the rotary valve is a portion of the crankcase itself, of particular importance, no wear should be allowed to take place. In a cross-flow engine, the transfer and exhaust ports are on opposite sides of the cylinder, and a deflector on the top of the piston directs
1512-413: Is accepted in most cases where cost, weight, and size are major considerations. The problem comes about because in "forward" running, the major thrust face of the piston is on the back face of the cylinder, which in a two-stroke particularly, is the coolest and best-lubricated part. The forward face of the piston in a trunk engine is less well-suited to be the major thrust face, since it covers and uncovers
1596-457: Is accomplished by engine programming to run (when the filter is full) in a manner that elevates exhaust temperature, in conjunction with an extra fuel injector in the exhaust stream that injects fuel to react with a catalyst element to burn off accumulated soot in the DPF filter, or through other methods. This is known as filter regeneration . Cleaning is also required as part of periodic maintenance, and it must be done carefully to avoid damaging
1680-422: Is attributed to Scottish engineer Dugald Clerk , who patented his design in 1881. However, unlike most later two-stroke engines, his had a separate charging cylinder. The crankcase -scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day . On 31 December 1879, German inventor Karl Benz produced a two-stroke gas engine, for which he received
1764-597: Is being phased out. Honda , for instance, ceased selling two-stroke off-road motorcycles in the United States in 2007, after abandoning road-going models considerably earlier. Due to their high power-to-weight ratio and ability to be used in any orientation, two-stroke engines are common in handheld outdoor power tools including leaf blowers , chainsaws , and string trimmers . Two-stroke diesel engines are found mostly in large industrial and marine applications, as well as some trucks and heavy machinery. Although
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#17327754845461848-574: Is common in on-road, off-road, and stationary two-stroke engines ( Detroit Diesel ), certain small marine two-stroke engines ( Gray Marine Motor Company , which adapted the Detroit Diesel Series 71 for marine use ), certain railroad two-stroke diesel locomotives ( Electro-Motive Diesel ) and large marine two-stroke main propulsion engines ( Wärtsilä ). Ported types are represented by the opposed piston design in which two pistons are in each cylinder, working in opposite directions such as
1932-432: Is that the two-stroke's crankcase is sealed and forms part of the induction process in gasoline and hot-bulb engines . Diesel two-strokes often add a Roots blower or piston pump for scavenging . The reed valve is a simple but highly effective form of check valve commonly fitted in the intake tract of the piston-controlled port. It allows asymmetric intake of the fuel charge, improving power and economy, while widening
2016-409: Is under every circumstance more efficient than cross-flow scavenging. In a uniflow engine, the mixture, or "charge air" in the case of a diesel, enters at one end of the cylinder controlled by the piston and the exhaust exits at the other end controlled by an exhaust valve or piston. The scavenging gas-flow is, therefore, in one direction only, hence the name uniflow. The design using exhaust valve(s)
2100-498: The EPA . Several manufacturers and retailers of diesel emissions defeat devices have been fined up to $ 1 million dollars. Two-stroke engine#Two-stroke diesel engine A two-stroke (or two-stroke cycle ) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston (one up and one down movement) in one revolution of the crankshaft. (A four-stroke engine requires four strokes of
2184-550: The European Union and some individual European countries, most Asian countries, and the rest of North and South America . Whilst few jurisdictions have explicitly made filters mandatory, the increasingly stringent emissions regulations that engine manufacturers must meet mean that eventually all on-road diesel engines will be fitted with them. In the European Union, filters are expected to be necessary to meet
2268-464: The Junkers Jumo 205 and Napier Deltic . The once-popular split-single design falls into this class, being effectively a folded uniflow. With advanced-angle exhaust timing, uniflow engines can be supercharged with a crankshaft-driven blower, either piston or Roots-type. The piston of this engine is "top-hat"-shaped; the upper section forms the regular cylinder, and the lower section performs
2352-512: The expansion chamber , such as the Suzuki SAEC and Honda V-TACS system. The result is an engine with better low-speed power without sacrificing high-speed power. However, as power valves are in the hot gas flow, they need regular maintenance to perform well. Direct injection has considerable advantages in two-stroke engines. In carburetted two-strokes, a major problem is a portion of the fuel/air mixture going directly out, unburned, through
2436-479: The oil reservoir does not depend on gravity. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab , German manufacturers DKW , Auto-Union , VEB Sachsenring Automobilwerke Zwickau , VEB Automobilwerk Eisenach , and VEB Fahrzeug- und Jagdwaffenwerk , and Polish manufacturers FSO and FSM . The Japanese manufacturers Suzuki and Subaru did
2520-428: The warning light and waits too long to operate the vehicle above 60 km/h (40 mph), the DPF may not regenerate properly, and continued operation past that point may spoil the DPF completely so it must be replaced. Some newer diesel engines, namely those installed in combination vehicles, can also perform what is called a Parked Regeneration, where the engine increases RPM to around 1400 while parked, to increase
2604-528: The 1960s due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was the piston could be made nearly flat or slightly domed, which allowed the piston to be appreciably lighter and stronger, and consequently to tolerate higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes, and compression losses. SAAB built 750- and 850-cc three-cylinder engines based on
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2688-407: The 1960s, especially for motorcycles, but for smaller or slower engines using direct injection, the deflector piston can still be an acceptable approach. This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel/air mixture strikes the cylinder head , then follows the curvature of
2772-838: The Euro.VI heavy truck engine emissions regulations currently under discussion and planned for the 2012-2013 time frame. In 2000, in anticipation of the future Euro 5 regulations PSA Peugeot Citroën became the first company to make filters standard on passenger cars. As of December 2008, the California Air Resources Board (CARB) established the 2008 California Statewide Truck and Bus Rule which—with variance according to vehicle type, size and usage—requires that on-road diesel heavy trucks and buses in California be retrofitted, repowered, or replaced to reduce particulate matter (PM) emissions by at least 85%. Retrofitting
2856-506: The Fe lattice to hold more oxygen. This advancement is significant because it allows the cleaning reaction to take place at the standard operating temperature of most diesel engines, removing the requirement for burning extra fuel or otherwise artificially heating the engine. The family of Mg doped catalysts, named Grindstaff catalysts after the chemist who started the work, has been the subject of much investigation across industry and academia with
2940-452: The German inventor of an early form in the mid-1920s, it became widely adopted in Germany country during the 1930s and spread further afield after World War II . Loop scavenging is the most common type of fuel/air mixture transfer used on modern two-stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop-scavenged, two-stroke engines. This operational feature
3024-584: The UK made changes to its MOT test requirements, including tougher scrutiny of diesel cars. One requirement was to have a properly fitted and working DPF. Driving without a DPF could incur a £1000 fine. Unlike a catalytic converter which is a flow-through device, a DPF retains bigger exhaust gas particles by forcing the gas to flow through the filter material before exiting; however, the DPF does not retain small particles. Maintenance-free DPFs oxidise or burn larger particles until they are small enough to pass through
3108-444: The attendant explosion risk from coal damp) use off-board regeneration if non-disposable filters are installed, with the regeneration stations sited in an area where non-permissible machinery is allowed. Many forklifts may also use off-board regeneration – typically mining machinery and other machinery that spend their operational lives in one location, which makes having a stationary regeneration station practical. In situations where
3192-423: The bore diameter for reasonable piston ring life. Beyond this, the piston rings bulge into the exhaust port and wear quickly. A maximum 70% of bore width is possible in racing engines, where rings are changed every few races. Intake duration is between 120 and 160°. Transfer port time is set at a minimum of 26°. The strong, low-pressure pulse of a racing two-stroke expansion chamber can drop the pressure to -7 psi when
3276-459: The combustion chamber, and then is deflected downward. This not only prevents the fuel/air mixture from traveling directly out the exhaust port, but also creates a swirling turbulence which improves combustion efficiency , power, and economy. Usually, a piston deflector is not required, so this approach has a distinct advantage over the cross-flow scheme (above). Often referred to as "Schnuerle" (or "Schnürle") loop scavenging after Adolf Schnürle,
3360-453: The crankshaft commonly spins in the same axis and direction as do the wheels i.e. "forward". Some of the considerations discussed here apply to four-stroke engines (which cannot reverse their direction of rotation without considerable modification), almost all of which spin forward, too. It is also useful to note that the "front" and "back" faces of the piston are - respectively - the exhaust port and intake port sides of it, and are not to do with
3444-415: The cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion , railway locomotives , and electricity generation . In a two-stroke engine, the exhaust gases transfer less heat to the cooling system than a four-stroke, which means more energy to drive the piston, and if present,
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3528-477: The diesel particulate filters of the trucks. No injuries occurred before the recall, though one grass fire was started. A similar recall was issued for 2005-2007 Jaguar S-Type and XJ diesels, where large amounts of soot became trapped in the DPF In affected vehicles, smoke and fire emanated from the vehicle underside, accompanied by flames from the rear of the exhaust. The heat from the fire could cause heating through
3612-537: The driver before filter restriction causes an issue with driveability or damage to the engine or filter develop. Regular filter maintenance is a necessity to remove ash build up, either through cleaning or replacement of the filter. Regeneration typically requires the vehicle to be driven continuously at 50-60mph (80-100km/h) for 30 to 45 minutes every few hundred miles/kilometers of city driving. Heavy duty pickup trucks have less stringent requirements for all three parameters, and Class 8 trucks significantly less. If
3696-425: The electrical requirement. Disposable paper cores are used in certain specialty applications, without a regeneration strategy. Coal mines are common users – the exhaust gas is usually first passed through a water trap to cool it, and then through the filter. Paper filters are also used when a diesel machine must be used indoors for short periods of time, such as on a forklift being used to install equipment inside
3780-400: The engine from end loads. Large two-stroke ship diesels are sometimes made to be reversible. Like four-stroke ship engines (some of which are also reversible), they use mechanically operated valves, so require additional camshaft mechanisms. These engines use crossheads to eliminate sidethrust on the piston and isolate the under-piston space from the crankcase. On top of other considerations,
3864-561: The engines with CARB-approved diesel particulate filters is one way to fulfill this requirement. In 2009 the American Recovery and Reinvestment Act provided funding to assist owners in offsetting the cost of diesel retrofits for their vehicles. Other jurisdictions have also launched retrofit programs, including: Inadequately maintained particulate filters on vehicles with diesel engines are prone to soot buildup, which can cause engine problems due to high back pressure. In 2018,
3948-415: The exhaust port in the cylinder, the hottest part of the engine, where piston lubrication is at its most marginal. The front face of the piston is also more vulnerable since the exhaust port, the largest in the engine, is in the front wall of the cylinder. Piston skirts and rings risk being extruded into this port, so having them pressing hardest on the opposite wall (where there are only the transfer ports in
4032-409: The exhaust port, and direct injection effectively eliminates this problem. Two systems are in use: low-pressure air-assisted injection and high-pressure injection. Since the fuel does not pass through the crankcase, a separate source of lubrication is needed. For the purpose of this discussion, it is convenient to think in motorcycle terms, where the exhaust pipe faces into the cooling air stream, and
4116-620: The exhaust stream, downstream of the turbo, or fuel injection into the engine cylinders on the exhaust stroke. This fuel and exhaust gas mixture passes through the Diesel Oxidation Catalyst (DOC) creating temperatures high enough to burn off the accumulated soot. Once the pressure drop across the DPF lowers to a calculated value, the process ends, until the soot accumulation builds up again. This works well for vehicles that drive longer distances with few stops compared to those that perform short trips with many starts and stops. If
4200-413: The fibers are "woven" into a monolith. Such cores have the advantage that an electrical current can be passed through the monolith to heat the core for regeneration purposes, allowing the filter to regenerate at low exhaust temperatures and/or low exhaust flow rates. Metal fiber cores tend to be more expensive than cordierite or silicon carbide cores, and are generally not interchangeable with them because of
4284-462: The filter develops too much pressure then the last type of regeneration must be used – a forced regeneration. This can be accomplished in two ways. The vehicle operator can initiate the regeneration via a dashboard mounted switch. Various signal interlocks, such as park brake applied, transmission in neutral, engine coolant temperature, and an absence of engine related fault codes are required (vary by OEM and application) for this process to initiate. When
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#17327754845464368-412: The filter is physically removed from the machine for regeneration there is also the advantage of being able to inspect the filter core on a daily basis (DPF cores for non-road applications are typically sized to be usable for one shift – so regeneration is a daily occurrence). Intentionally removing or tampering with a DPF device, known as variously as "deleting", "defeating" or "tuning", is prohibited by
4452-538: The filter, though often particles "clump" together in the DPF reducing the overall particle count as well as overall mass. There are a variety of diesel particulate filter technologies on the market. Each is designed around similar requirements: The most common filter is made of cordierite (a ceramic material that is also used as catalytic converter supports (cores)). Cordierite filters provide excellent filtration efficiency, are relatively inexpensive, and have thermal properties that make packaging them for installation in
4536-407: The filter. Failure of fuel injectors or turbochargers resulting in contamination of the filter with raw diesel or engine oil can also necessitate cleaning. The regeneration process occurs at road speeds higher than can generally be attained on city streets; vehicles driven exclusively at low speeds in urban traffic can require periodic trips at higher speeds to clean out the DPF. If the driver ignores
4620-668: The formation of fine particles. Diesel particulate filtering was first considered in the 1970s due to concerns regarding the impacts of inhaled particulates. Particulate filters have been in use on non-road machines since 1980, and in automobiles since 1985. Historically medium and heavy duty diesel engine emissions were not regulated until 1987 when the first California Heavy Truck rule was introduced capping particulate emissions at 0.60 g/BHP Hour. Since then, progressively tighter standards have been introduced for light- and heavy-duty roadgoing diesel-powered vehicles and for off-road diesel engines. Similar regulations have also been adopted by
4704-413: The fresh intake charge into the upper part of the cylinder, pushing the residual exhaust gas down the other side of the deflector and out the exhaust port. The deflector increases the piston's weight and exposed surface area, and the fact that it makes piston cooling and achieving an effective combustion chamber shape more difficult is why this design has been largely superseded by uniflow scavenging after
4788-445: The fuel-air mix less completely. Diesel particulate matter resulting from the incomplete combustion of diesel fuel produces soot ( black carbon ) particles. These particles include tiny nanoparticles —smaller than one micrometre (one micron). Soot and other particles from diesel engines worsen the particulate matter pollution in the air and are harmful to health. New particulate filters can capture from 30% to greater than 95% of
4872-407: The harmful soot. With an optimal diesel particulate filter (DPF), soot emissions may be decreased to 0.001 g/km or less. The quality of the fuel also influences the formation of these particles. For example, a high sulphur content diesel produces more particles. Lower sulphur fuel produces fewer particles, and allows use of particulate filters. The injection pressure of diesel also influences
4956-443: The intake and exhaust ports in some two-stroke designs can also allow some amount of unburned fuel vapors to exit in the exhaust stream. The high combustion temperatures of small, air-cooled engines may also produce NO x emissions. Two-stroke gasoline engines are preferred when mechanical simplicity, light weight, and high power-to-weight ratio are design priorities. By mixing oil with fuel, they can operate in any orientation as
5040-485: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=OPF&oldid=1224539824 " Category : Disambiguation pages Hidden categories: Articles containing German-language text Short description is different from Wikidata All article disambiguation pages All disambiguation pages Gasoline particulate filter Wall-flow diesel particulate filters usually remove 85% or more of
5124-402: The machine is either plugged into a wall/floor mounted regeneration station, or the filter is removed from the machine and placed in the regeneration station). Off-board regeneration is not suitable for on-road vehicles, except in situations where the vehicles are parked in a central depot when not in use. Off-board regeneration is mainly used in industrial and mining applications. Coal mines (with
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#17327754845465208-475: The model year. The Monte Carlo Rally variant, 750-cc (with a filled crankshaft for higher base compression), generated 65 hp. An 850-cc version was available in the 1966 SAAB Sport (a standard trim model in comparison to the deluxe trim of the Monte Carlo). Base compression comprises a portion of the overall compression ratio of a two-stroke engine. Work published at SAE in 2012 points that loop scavenging
5292-399: The oil pump of a modern two-stroke may not work in reverse, in which case the engine suffers oil starvation within a short time. Running a motorcycle engine backward is relatively easy to initiate, and in rare cases, can be triggered by a back-fire. It is not advisable. Model airplane engines with reed valves can be mounted in either tractor or pusher configuration without needing to change
5376-487: The other - the inlet pipe having passage to the crankcase only when the two cutouts coincide. The crankshaft itself may form one of the members, as in most glow-plug model engines. In another version, the crank disc is arranged to be a close-clearance fit in the crankcase, and is provided with a cutout that lines up with an inlet passage in the crankcase wall at the appropriate time, as in Vespa motor scooters. The advantage of
5460-434: The piston covering and uncovering the ports as it moves up and down in the cylinder. In the 1970s, Yamaha worked out some basic principles for this system. They found that, in general, widening an exhaust port increases the power by the same amount as raising the port, but the power band does not narrow as it does when the port is raised. However, a mechanical limit exists to the width of a single exhaust port, at about 62% of
5544-440: The piston is at bottom dead center, and the transfer ports nearly wide open. One of the reasons for high fuel consumption in two-strokes is that some of the incoming pressurized fuel-air mixture is forced across the top of the piston, where it has a cooling action, and straight out the exhaust pipe. An expansion chamber with a strong reverse pulse stops this outgoing flow. A fundamental difference from typical four-stroke engines
5628-940: The piston to complete a power cycle, in two crankshaft revolutions.) In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust (or scavenging ) functions occurring at the same time. Two-stroke engines often have a higher power-to-weight ratio than a four-stroke engine, since their power stroke occurs twice as often. Two-stroke engines can also have fewer moving parts , and thus be cheaper to manufacture and weigh less. In countries and regions with stringent emissions regulation, two-stroke engines have been phased out in automotive and motorcycle uses. In regions where regulations are less stringent, small displacement two-stroke engines remain popular in mopeds and motorcycles. They are also used in power tools such as chainsaws and leaf blowers . The first commercial two-stroke engine involving cylinder compression
5712-412: The plugs force the exhaust gas flow through the wall and the particulate collects on the inlet face. The second most popular filter material is silicon carbide , or SiC . It has a higher (2700 °C) melting point than cordierite, however, it is not as stable thermally, making packaging an issue. Small SiC cores are made of single pieces, while larger cores are made in segments, which are separated by
5796-550: The power band. Such valves are widely used in motorcycle, ATV, and marine outboard engines. The intake pathway is opened and closed by a rotating member. A familiar type sometimes seen on small motorcycles is a slotted disk attached to the crankshaft , which covers and uncovers an opening in the end of the crankcase, allowing charge to enter during one portion of the cycle (called a disc valve). Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members with suitable cutouts arranged to rotate one within
5880-466: The principles remain the same, the mechanical details of various two-stroke engines differ depending on the type. The design types vary according to the method of introducing the charge to the cylinder, the method of scavenging the cylinder (exchanging burnt exhaust for fresh mixture) and the method of exhausting the cylinder. Piston port is the simplest of the designs and the most common in small two-stroke engines. All functions are controlled solely by
5964-413: The range of 350 to 450 °C by use of a fuel-borne catalyst. The actual temperature of soot burn-out will depend on the chemistry employed. In the mid-2010s, scientists at 3M developed a magnesium doped version of traditional iron based catalysts which lowered the temperature required for particulate matter oxidation to just over 200 °C. The lower reaction temperature is made possible by the dopant allowing
6048-494: The regeneration cycle. The additional fuel can be supplied by a metering pump . Running the cycle too often while keeping the back pressure in the exhaust system low will result in high fuel consumption. Not running the regeneration cycle soon enough increases the risk of engine damage and/or uncontrolled regeneration ( thermal runaway ) and possible DPF failure. Diesel particulate matter burns when temperatures above 600 °C are attained. This temperature can be reduced to somewhere in
6132-821: The same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, due to increasingly stringent regulation of air pollution . Eastern Bloc countries continued until around 1991, with the Trabant and Wartburg in East Germany. Two-stroke engines are still found in a variety of small propulsion applications, such as outboard motors , small on- and off-road motorcycles , mopeds , motor scooters , motorized bicycles , tuk-tuks , snowmobiles , go-karts , RC cars , ultralight and model airplanes. Particularly in developed countries, pollution regulations have meant that their use for many of these applications
6216-409: The soot accumulation reaches a level that is potentially damaging to the engine or the exhaust system, the solution involves a garage using a computer program to run a regeneration of the DPF manually. When a regeneration occurs, the soot is turned to gasses and ash of which some remains in the filter. This will increase restriction through the filter and can result in a blockage. Warnings are given to
6300-443: The soot buildup on the DPF walls. Active regeneration happens while the vehicle is in use, when low engine load and lower exhaust gas temperatures inhibit the naturally occurring passive regeneration. Sensors upstream and downstream of the DPF (or a differential pressure sensor) provide readings that initiate a metered addition of fuel into the exhaust stream. There are two methods to inject fuel, either downstream injection directly into
6384-401: The soot, and under certain conditions can attain soot removal efficiencies approaching 100%. Some filters are single-use, intended for disposal and replacement once full of accumulated ash. Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures. This
6468-425: The temperature of the exhaust. Diesel engines produce a variety of particles during the combustion of the fuel/air mix due to incomplete combustion. The composition of the particles varies widely dependent upon engine type, age, and the emissions specification that the engine was designed to meet. Two-stroke diesel engines produce more particulate per unit of power than do four-stroke diesel engines, as they burn
6552-424: The tightening of emissions regulations on particulate matter world wide. In some cases, in the absence of a fuel-borne catalyst, the combustion of the particulate matter can raise temperatures so high, that they are above the structural integrity threshold of the filter material, which can cause catastrophic failure of the substrate. Various strategies have been developed to limit this possibility. Note that unlike
6636-520: The top or bottom of the piston. Regular gasoline two-stroke engines can run backward for short periods and under light load with little problem, and this has been used to provide a reversing facility in microcars , such as the Messerschmitt KR200 , that lacked reverse gearing. Where the vehicle has electric starting, the motor is turned off and restarted backward by turning the key in the opposite direction. Two-stroke golf carts have used
6720-431: The transmission tunnel to the interior, melting interior components and potentially causing interior fires. Regeneration is the process of burning off (oxidizing) the accumulated soot from the filter. This is done either passively (from the engine's exhaust heat in normal operation or by adding a catalyst to the filter) or actively introducing very high heat into the exhaust system. On-board active filter management can use
6804-569: The vehicle is often driven in cities the DPF may become clogged, causing a reduction in power and acceleration either passively due to increased exhaust pressure or actively due to vehicle going into "limp/turtle mode" as it tries to prevent engine and turbo damage. Once clogged both passive and active regeneration may become ineffective. DPF may be unclogged by high temperature pressure washing (not officially recommended) and/or burn-off oven . In 2011, Ford recalled 37,400 F-Series trucks with diesel engines after fuel and oil leaks caused fires in
6888-488: The vehicle simple. The major drawback is that cordierite has a relatively low melting point (about 1200 °C) and cordierite substrates have been known to melt during filter regeneration. This is mostly an issue if the filter has become loaded more heavily than usual, and is more of an issue with passive systems than with active systems, unless there is a system breakdown. Cordierite filter cores look like catalytic converter cores that have had alternate channels plugged –
6972-815: The wall and the particulate collects on the inlet face. The characteristics of the wall flow diesel particulate filter substrate are: Fibrous ceramic filters are made from several different types of ceramic fibers that are mixed together to form a porous medium. This medium can be formed into almost any shape and can be customized to suit various applications. The porosity can be controlled in order to produce high flow, lower efficiency or high efficiency lower volume filtration. Fibrous filters have an advantage over wall flow design of producing lower back pressure. Fibrous ceramic filters remove carbon particulates almost completely, including fine particulates less than 100 nanometres (nm) diameter with an efficiency of greater than 95% in mass and greater than 99% in number of particles over
7056-541: Was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ, and Walter Kaaden. Loop scavenging, disc valves, and expansion chambers worked in a highly coordinated way to significantly increase the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha, and Kawasaki. Suzuki and Yamaha enjoyed success in Grand Prix motorcycle racing in
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